1. Field of the Invention
This invention relates to a method of temporarily securing a die to a burn-in carrier for the purpose of burn-in and testing of the die. More specifically, this invention relates to a method of temporarily securing a die to a burn-in carrier through the use of adhesive tape for the purpose of burn-in and testing of the die.
2. State of the Art
Integrated circuit memory devices, such as dynamic random access memories (DRAMS) and static random access memories (SRAMS) are tested during manufacture and often prior to use. Such testing is for the purpose of insuring that only known good dies are subsequently used.
One of the test procedures which is used to determine the viability of integrated semiconductor circuits is a burn-in procedure. The burn-in test is intended to stress the electrical interconnection of the die and drive any contaminants in the body of the die into the active circuitry, thus causing failure. This test is based on data indicating that dice that are prone to these types of failures will actually malfunction in the early part of their lifetime. By conducting burn-in tests, the early failures of the dice are detected and only known good dice are subsequently used in applications.
In the testing of a die prior to encapsulation, temporary electrical connection must be effected between the die and a test fixture. This is typically done by connecting the test fixture to the die using the bond pads of the die through the use of wire bonds or tape automated bonding. As is evident, the testing of an unpackaged or bare die requires a significant amount of handling. Since the test package must be separated from the die, the temporary packaging may be more complicated than either standard discrete packaging or multichip module packaging. The package must be compatible with any desired test and burn-in procedures without damaging the die at the bond pads or elsewhere during any such test or burn-in procedure.
In U.S. Pat. No. 4,899,107, a reusable burn-in test fixture for discrete tape automated bonding (TAB) a die is disclosed. The fixture consists of two halves, one of which is a die cavity plate for receiving semiconductor dies as the units under test and the other half establishes electrical contact with the dice and with the burn-in oven. The dice are held in position within the carrier by being resiliently mounted therein.
In U.S. Pat. No. 5,408,190, a reusable burn-in test fixture for discrete dice is disclosed. The reusable burn-in test fixture comprises two halves, the first half containing a cavity in which a die is inserted. As disclosed, a precured RTV silicone backing strip is used to retain a die in a face-up position in the carrier. The precured RTV strip, commonly known as a “gel pack,” exhibits a static charge and coefficient of friction sufficient to hold an intermediate substrate in place without the use of adhesive and elastomerically biases the die against the cover plate of the test fixture.
In U.S. Pat. No. 5,336,649, a precured RTV silicone strip, “gel pack,” is used for temporarily securing the die in place within a package body. The RTV silicone strip exhibits a static charge and coefficient of friction sufficient to hold the die in place within a burn-in carrier. Another embodiment discloses the use of a tape type die attach adhesive, known under the trademark of E.I. Du Pont de Nemours of Wilmington, Del. as Kapton QL Die Attach Adhesive, to hold the die in place during burn-in. The adhesive is heated, but for a shorter time than for a permanently packaged die. This allows a standard process setup to be used for temporary die attachment while permitting the adhesive attachment of the die to be readily overcome subsequent to testing and burn-in. Also disclosed is the use of water soluble hot melt glass, a thermoplastic material, to temporarily hold the die during testing and burn-in. After testing, the hot melt glass is removed by dissolving it using deionized water, thereby freeing the die from the package. In yet another instance, the die may be adhesively bonded to the carrier through the use of a sugar and water solution. After testing, the package including the die is placed in deionized water, which causes the sugar to dissolve, thereby freeing the die from the package.
However, these prior types of die attachment techniques have inherent problems. They either require specific types of mechanical mounting arrangements to be designed into the burn-in carrier, or require that the silicone “gel pack” exhibit sufficient electrostatic charge to retain the die in the burn-in carrier, or require the careful spraying of the adhesive in the burn-in carrier to minimize overspray of the adhesive, or require the use of a water cleaning solution after testing and burn-in to remove the adhesive remnants.